A milking system is one of the most important components on a dairy farm, for it is used more hours per year than any other type of equipment. A key component of a milking system is a vacuum pump, which is used to remove air from the milking system pipelines to create a partial vacuum. In a conventional vacuum milking system, the vacuum pump runs at full speed all the time, regardless of air demands. A vacuum regulator is generally used to regulate the desired vacuum level by admitting external air, as required, when the vacuum level reaches a predetermined setting. The nominal vacuum levels normally used for milking usually are selected to be in the range from 40 to 50 kPa, but vacuum fluctuations can occur in the system, as when a milking unit falls off the cow being milked, or when the system develops an air leak. It is essential that such fluctuations be limited to enable the vacuum system to meet ASAE standards as well as other standards. This is difficult to achieve, because such incidents can cause airflow in the system to increase over what is needed when the system is operating properly. To compensate for such variations, the size of the vacuum pump is selected to provide the desired vacuum level even when there is a large amount of leakage, and the vacuum regulator compensates vacuum fluctuations. Thus, for example, a vacuum pump operates at a constant rate sufficient to maintain a predetermined vacuum level in a reservoir even under leakage conditions, and a vacuum regulator connected to the reservoir admits air as required to control the vacuum level during normal operating conditions.
In such prior systems, if there is an increase in airflow through the milking system, airflow through the vacuum regulator is reduced so that the reservoir maintains the required vacuum level in the milking line. Ideally, in such systems, increases in the airflow in the milking system should result in decreases in the airflow through the regulator, and these should be about equal to cancel each other and to maintain vacuum equilibrium in the reservoir. The problem with this arrangement is that only a small portion of the vacuum pump capacity is actually needed for milking, with majority of the airflow passing through the regulator. In such arrangements, the capacity of the vacuum pump always exceeds the capacity needed to milk cows or to wash the milking system, and the pump always runs at full speed and full load, regardless of the actual need for vacuum.
Particularly, for modern automatic robotic milking systems, where animals may visit the automatic milking machine at will, the vacuum need may vary substantially over time, not only due to leakage or other incidents, but also for the reason that animals arrive at irregular intervals to the automatic milking system.
A recent improvement over the foregoing conventional system is described in U.S. Pat. No. 5,284,180, which discloses a system for varying the speed of a vacuum pump to maintain the required, vacuum level and stability in the system. In this patent, a vacuum level controlling system utilizes a two-level controller combined with an adjustable speed motor drive for the pump.
U.S. Pat. No. 5,960,763 describe a system and method, which supplies different vacuum levels depending on if the milking machine, is in washing or milking mode. It is possible to select which mode should be used at any time.
None of the above patents concerns the specific problems associated with robotic milking systems, e.g. animals arriving at irregular intervals to be milked.
A further problem is how to achieve better surveillance and monitoring of the workings of the vacuum pump system.
There is, therefore, a need for an automatic control system, for a vacuum pump in a milking system to provide an improved vacuum control system, for reducing electrical energy consumption, which will meet the needs of modern dairy farms.